3 The Culprits 2: Higher Temperatures, Polar Stratospheric Clouds and a Changing Climate

For a long time, depletion of the ozone layer and climate change were treated by legal agreements as two separate problems. But now the causes and effects of these two global environmental threats are seen by scientists, policy makers and the private sector as being inextricably linked, as indeed are the solutions to the problems.

This graph shows total ozone and stratospheric temperatures over the Arctic since 1979. Changes in ozone amounts closely follow temperature, with colder temperatures resulting in more polar stratospheric clouds that intensify ozone destruction. See also www.vitalgraphics.net/ozone: (questions on the scientific assessment 2006 update, figure Q18–1–20) Radiative forcing of climate change from atmospheric gas changes.
Ozone depletion and climate change are linked in many ways, through their effects on physical and chemical processes in the atmosphere, as well as interaction between the atmosphere and the rest of the global ecosystem. Changes in temperature and other natural and human-induced climatic factors such as cloud cover, winds and precipitation impact directly and indirectly on the scale of the chemical reactions that fuel destruction of the ozone in the stratosphere. Recent research indicates that climate change by 2030 may surpass CFCs as the main cause of overall ozone loss.

On the other hand the fact that ozone absorbs solar radiation means it counts as a greenhouse gas (GHG), much as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and halogen source gases. Stratospheric ozone depletion and increases in global ozone near the Earth’s surface (tropospheric ozone) in recent decades contribute to climate change. The 2006 report by the Environmental Effects Assessment Panel takes this into account, focusing its assessment on interaction with climate change (see references for full report).

Above all the evidence suggests that continued intense cooperation is needed between Parties to the Montreal and Kyoto Protocols for both of these international agreements to succeed, and for a sustainable future. The situation calls for joint responsibility, coordinated policies and integrated solutions that support the objectives of both treaties.

Major links between ozone depletion and climate change

Many of the man-made ozone depleting chemicals (e.g. CFCs and HCFCs) and their replacements (e.g. HFCs) are potent greenhouse gases.

The build-up of GHGs, including ODS and their replacements, is known to enhance warming of the lower atmosphere, called the troposphere (where weather systems occur) and is also expected, on balance, to lead to cooling of the stratosphere.

Stratospheric cooling creates a more favourable environment for the formation of polar stratospheric clouds, which are a key factor in the development of polar ozone holes. Cooling of the stratosphere due to the build-up of GHGs and associated climate change is therefore likely to exacerbate destruction of the ozone layer.

The troposphere and stratosphere are not independent of one another. Changes in the circulation and chemistry of one can affect the other. Changes in the troposphere associated with climate change may affect functions in the stratosphere. Similarly changes in the stratosphere due to ozone depletion can affect functions in the troposphere in intricate ways that make it difficult to predict the cumulative effects.

Source: EIA (2006). Turning up the Heat

 
 

Story ideas
#3a. Climate change story: Just as we appear to be making progress turning back ozone depletion, scientists believe increasingly that climate change is itself a driver of ozone depletion and in fact may surpass CFCs as the leading cause of ozone depletion by 2030.

#3b. Climate change story (different spin): Increased warming in certain parts of the world threatens to increase demand for refrigerants, which would further deplete the ozone layer and further accelerate climate change.

*Adapted from Merri Weinger. Teacher's guide on basic environmental health. [19]

Now let’s take a more detailed look at some methods, effectively utilised whilst conducting training.

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